修复 OAuth/SetupToken 转发请求体重排并增加调试开关

backend/internal/pkg/antigravity/request_transformer.go

@@ -275,21 +275,6 @@ func filterOpenCodePrompt(text string) string {
 	return ""
 }
 
-// systemBlockFilterPrefixes 需要从 system 中过滤的文本前缀列表
-var systemBlockFilterPrefixes = []string{
-	"x-anthropic-billing-header",
-}
-
-// filterSystemBlockByPrefix 如果文本匹配过滤前缀，返回空字符串
-func filterSystemBlockByPrefix(text string) string {
-	for _, prefix := range systemBlockFilterPrefixes {
-		if strings.HasPrefix(text, prefix) {
-			return ""
-		}
-	}
-	return text
-}
-
 // buildSystemInstruction 构建 systemInstruction（与 Antigravity-Manager 保持一致）
 func buildSystemInstruction(system json.RawMessage, modelName string, opts TransformOptions, tools []ClaudeTool) *GeminiContent {
 	var parts []GeminiPart
@@ -306,8 +291,8 @@ func buildSystemInstruction(system json.RawMessage, modelName string, opts Trans
 				if strings.Contains(sysStr, "You are Antigravity") {
 					userHasAntigravityIdentity = true
 				}
-				// 过滤 OpenCode 默认提示词和黑名单前缀
-				filtered := filterSystemBlockByPrefix(filterOpenCodePrompt(sysStr))
+				// 过滤 OpenCode 默认提示词
+				filtered := filterOpenCodePrompt(sysStr)
 				if filtered != "" {
 					userSystemParts = append(userSystemParts, GeminiPart{Text: filtered})
 				}
@@ -321,8 +306,8 @@ func buildSystemInstruction(system json.RawMessage, modelName string, opts Trans
 						if strings.Contains(block.Text, "You are Antigravity") {
 							userHasAntigravityIdentity = true
 						}
-						// 过滤 OpenCode 默认提示词和黑名单前缀
-						filtered := filterSystemBlockByPrefix(filterOpenCodePrompt(block.Text))
+						// 过滤 OpenCode 默认提示词
+						filtered := filterOpenCodePrompt(block.Text)
 						if filtered != "" {
 							userSystemParts = append(userSystemParts, GeminiPart{Text: filtered})
 						}

backend/internal/pkg/antigravity/request_transformer_test.go

@@ -2,7 +2,10 @@ package antigravity
 
 import (
 	"encoding/json"
+	"strings"
 	"testing"
+
+	"github.com/stretchr/testify/require"
 )
 
 // TestBuildParts_ThinkingBlockWithoutSignature 测试thinking block无signature时的处理
@@ -349,3 +352,51 @@ func TestBuildGenerationConfig_ThinkingDynamicBudget(t *testing.T) {
 		})
 	}
 }
+
+func TestTransformClaudeToGeminiWithOptions_PreservesBillingHeaderSystemBlock(t *testing.T) {
+	tests := []struct {
+		name   string
+		system json.RawMessage
+	}{
+		{
+			name:   "system array",
+			system: json.RawMessage(`[{"type":"text","text":"x-anthropic-billing-header keep"}]`),
+		},
+		{
+			name:   "system string",
+			system: json.RawMessage(`"x-anthropic-billing-header keep"`),
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			claudeReq := &ClaudeRequest{
+				Model:  "claude-3-5-sonnet-latest",
+				System: tt.system,
+				Messages: []ClaudeMessage{
+					{
+						Role:    "user",
+						Content: json.RawMessage(`[{"type":"text","text":"hello"}]`),
+					},
+				},
+			}
+
+			body, err := TransformClaudeToGeminiWithOptions(claudeReq, "project-1", "gemini-2.5-flash", DefaultTransformOptions())
+			require.NoError(t, err)
+
+			var req V1InternalRequest
+			require.NoError(t, json.Unmarshal(body, &req))
+			require.NotNil(t, req.Request.SystemInstruction)
+
+			found := false
+			for _, part := range req.Request.SystemInstruction.Parts {
+				if strings.Contains(part.Text, "x-anthropic-billing-header keep") {
+					found = true
+					break
+				}
+			}
+
+			require.True(t, found, "转换后的 systemInstruction 应保留 x-anthropic-billing-header 内容")
+		})
+	}
+}